diff options
| -rw-r--r-- | include/clang/AST/Decl.h | 8 | ||||
| -rw-r--r-- | lib/CodeGen/CGCall.cpp | 13 | ||||
| -rw-r--r-- | lib/Sema/SemaDecl.cpp | 5 |
3 files changed, 25 insertions, 1 deletions
diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h index f8ee70b752..3214b653b9 100644 --- a/include/clang/AST/Decl.h +++ b/include/clang/AST/Decl.h @@ -682,6 +682,7 @@ private: bool HasWrittenPrototype : 1; bool IsDeleted : 1; bool IsTrivial : 1; // sunk from CXXMethodDecl + bool HasImplicitReturnZero : 1; // Move to DeclGroup when it is implemented. SourceLocation TypeSpecStartLoc; @@ -722,6 +723,7 @@ protected: SClass(S), IsInline(isInline), C99InlineDefinition(false), IsVirtualAsWritten(false), IsPure(false), HasInheritedPrototype(false), HasWrittenPrototype(true), IsDeleted(false), IsTrivial(false), + HasImplicitReturnZero(false), TypeSpecStartLoc(TSSL), EndRangeLoc(L), TemplateOrSpecialization() {} virtual ~FunctionDecl() {} @@ -798,6 +800,12 @@ public: bool isTrivial() const { return IsTrivial; } void setTrivial(bool IT) { IsTrivial = IT; } + /// Whether falling off this function implicitly returns null/zero. + /// If a more specific implicit return value is required, front-ends + /// should synthesize the appropriate return statements. + bool hasImplicitReturnZero() const { return HasImplicitReturnZero; } + void setHasImplicitReturnZero(bool IRZ) { HasImplicitReturnZero = IRZ; } + /// \brief Whether this function has a prototype, either because one /// was explicitly written or because it was "inherited" by merging /// a declaration without a prototype with a declaration that has a diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp index 88a5eeb68e..d7019b605d 100644 --- a/lib/CodeGen/CGCall.cpp +++ b/lib/CodeGen/CGCall.cpp @@ -505,6 +505,19 @@ void CodeGenModule::ConstructAttributeList(const CGFunctionInfo &FI, void CodeGenFunction::EmitFunctionProlog(const CGFunctionInfo &FI, llvm::Function *Fn, const FunctionArgList &Args) { + // If this is an implicit-return-zero function, go ahead and + // initialize the return value. TODO: it might be nice to have + // a more general mechanism for this that didn't require synthesized + // return statements. + if (const FunctionDecl* FD = dyn_cast<FunctionDecl>(CurFuncDecl)) { + if (FD->hasImplicitReturnZero()) { + QualType RetTy = FD->getResultType().getUnqualifiedType(); + const llvm::Type* LLVMTy = CGM.getTypes().ConvertType(RetTy); + llvm::Constant* Zero = CGM.getLLVMContext().getNullValue(LLVMTy); + Builder.CreateStore(Zero, ReturnValue); + } + } + // FIXME: We no longer need the types from FunctionArgList; lift up and // simplify. diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp index 7ab7356aa0..9b6de12bb2 100644 --- a/lib/Sema/SemaDecl.cpp +++ b/lib/Sema/SemaDecl.cpp @@ -3501,8 +3501,11 @@ Sema::DeclPtrTy Sema::ActOnFinishFunctionBody(DeclPtrTy D, StmtArg BodyArg, Stmt *Body = BodyArg.takeAs<Stmt>(); if (FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(dcl)) { FD->setBody(Body); - if (!FD->isMain()) + if (FD->isMain()) // C and C++ allow for main to automagically return 0. + // Implements C++ [basic.start.main]p5 and C99 5.1.2.2.3. + FD->setHasImplicitReturnZero(true); + else CheckFallThroughForFunctionDef(FD, Body); if (!FD->isInvalidDecl()) |